Fuel Pressure Leak Down Test
- Remove cap from pressure test port in fuel rail. See Figure . Connect a 0-60 psi (0-4.22 kg/cm2 ) fuel pressure gauge to pressure fitting on fuel rail. Start and run engine at idle.
- Turn engine off and note fuel pressure reading on gauge. Leave fuel pressure gauge connected. Allow 30 minutes to elapse and then compare fuel pressure reading to reading taken when engine was off.
- A pressure drop up to 20 psi (1.4 kg/cm2
) to a range of 19-39 psi (1.3 2.7 kg/cm2
) is within specification. If pressure drop is correct, the fuel pump outlet check valve and fuel pressure regulator are operating correctly.CAUTION: Fuel pressure will rise as high as 95 psi (6.7 kg/cm2 ) when fuel return line is pinched shut. Turn engine off IMMEDIATELY after pinching off fuel return line.
- If pressure drop is greater than 20 psi (1.4 kg/cm2 ), restart vehicle and let engine idle. Momentarily pinch shut hose section of fuel return line and IMMEDIATELY turn engine off. Note pressure reading on gauge. Allow 30 minutes to elapse and then compare fuel pressure reading to reading taken when engine was turned off.
- If fuel pressure drops to about 20 psi (1.4 kg/cm2 ), replace fuel pressure regulator. If fuel pressure drops more than 20 psi (1.4 kg/cm2 ), fuel pressure is bleeding off past outlet check valve in fuel pump. Fuel pump must be replaced.